1. Field of the Invention
The invention relates to a rechargeable electric storage battery with liquid sodium as the negative and liquid sulfur, absorbed in graphite, as the positive electrochemical, as well as sodium ion-conducting solid electrolytes, which have metallic housings.
2. Description of the Prior Art
The principle of electric sodium/sulfur batteries is known (B. Fischer, H. Meinhold, Elektrische Energietechnik 24, 1979, pages 1-6). Such batteries consist in substance of several individual cells which can be constructed with the sodium ion conductor (.beta.-Al.sub.2 O.sub.3) in the form of tubes closed at one end. In the reaction of sulfur (cathode) with sodium (anode) occurring in the cell, an electric current is generated. The sodium or the sulfur, respectively, can be disposed either in the interior or outside of the tube. The tube which consists of .beta.-Al.sub.2 O.sub.3 functions as an electrolyte and a separator between the negative and the positive active material. The sulfur is usually absorbed in a graphite matrix. Individual cells are built and are electrically wired to each other in series or parallel. Such individual design requires relatively large space, and a separate housing is required for each cell. As a positive result, the volumetric and gravimetric energy density becomes worse. A remedy was obtained in part by changing the cell concept and either several tubes were put in a common outer sodium reservoir (German Pat. No. 2,456,021) or the shape of the ceramic was changed into plates or concentric tubes (German Pat. No. 2,518,923). These cell arrangements, however, have the disadvantage that the current paths between the cells are relatively long, which can add up to represent considerable ohmic losses. In addition, either the shape of the ceramic or the type of electrical interconnection is expensive, which leads to a considerable cost increase in the production of the battery.